The invention disclosed herein relates to detection of, and accounting for, unauthorized postage printing in an electronic postage meter, particularly a postage meter having print wheels that are not locked against rotation when power to the postage meter is switched off.
One type of known electronic postage meter includes a plurality of individually settable print wheels mounted to a print drum which is rotated to print the postage value of the digits set in the print wheels. To prevent fraudulent postage printing, i.e., printing without accounting for the postage, the postage meter accounts for print cycles (each rotation of the print drum) both when power to the postage meter is on and off. Manual rotation of the print wheels and the print drum are prevented by the drive mechanisms for the print wheels and drum when power to the postage meter is on, thereby preventing postage printing without accounting while power is on. To deter fraudulent postage printing when power to the meter is off, the meter includes a cover or shroud which limits access to the print wheels and print drum. However, the cover or shroud does not lock the print drum or the print wheels.
It has been found that fraudulent postage printing can be prevented by providing a locking mechanism that locks the print wheels against rotation when power to the postage meter is off. Postage printing by the locked print wheels may be accounted for by recording the digit values of the print wheels when power to the meter is switched off and by detecting, when power is switched on again, rotation of the print drum which occurred when power to the meter was off. In this way, postage values can not be set when the meter is off, but if the print drum is rotated when the meter is off, postage will be accounted.
The tamper-resistant cover or shroud referred to above while deterring tampering, performs no postage accounting function. Therefore, a postage meter in which the print wheels are not locked against rotation when power to the postage meter is off will not account for postage printed when the meter is off since the setting of the print wheels for each print cycle will not be unequivocally known. A postage meter of the type described above may not include a print wheel locking mechanism due to space considerations, such as in the postage meter described in the above-referenced patent applications.
The disclosures of the following U.S. patents are incorporated herein by reference: U.S. Pat. Nos. 4,630,210, 4,631,681, 4,635,205, 4,636,959, 4,646,635, 4,665,353, 4,638,732, 4,774,446 and 4,643,089, all of Salazar et al. and U.S. Pat. No. 4,731,728 of Muller. All of those patents are assigned to the assignee of this application. Those patents disclose an electronic postage meter including a plurality of print wheels mounted to a print drum.
There is thus a need to detect and account for postage printed by a postage meter that does not include a print wheel locking mechanism which prevents print wheel rotation while power to the postage meter was off.